One of the first things some of Harper's teammates noticed when he made his Major League debut at 19 back in 2012 was his batting practices. They'd never seen a player swing the bat harder or hit the ball farther in batting practice.
As word got around, players on opposing teams would stop and stare as Harper sprayed rockets to every corner of the park. They could not imagine anyone putting so much effort into something so routine, something most players use to prepare for that day's game.
Harper apparently, at least in those early days, saw it as a contest within a contest, and he was going to establish himself then and there as the best at that, too.